The present invention relates to the throttled teeming of molten metal from teeming vessels into a receiver, such as, for example, the mold of a continuous caster. More particularly, the present invention relates to an improved form of gate and pour tube holder for use in sliding gate valves of the throttling type.
In U.S. Pat. No. 4,415,103, issued Nov. 15, 1983 to E. P. Shapland, et al., there is described one form of sliding gate valve of the type in which refractory gates can be moved sequentially into and out of an operative position with respect to the flow opening from a metal teeming vessel, such as a tundish, and which, in such operative position, can be selectively moved in order to throttle the flow of metal from the vessel. In such valve apparatus, a top plate containing a flow passage is fixedly positioned in communication with the vessel flow opening. The valve apparatus also contains a pour tube assembly including a pour tube for conducting metal flow from the valve and into the receiver, and a pour tube holder for replaceably positioning the pour tube in operatively fixed, axially spaced relation from the top plate flow passage. The gates are operative to move transversely between the top plate and the tube holder across the metal flow stream and thereby control the flow of metal passed through the valve apparatus by varying the effective size of the flow passage by displacing the gate opening with respect to the top plate flow passage.
Problems have been experienced in the utilization of throttling gate valves, particularly in the production of aluminum-killed steels which are high quality steels whose utility is prominent where metal surface quality and drawing capability are critical. The problems are most apparent during the operation of valve apparatus of the described type, particularly under partial, or throttled flow conditions, when deposits of alumina accumulate in the gate opening tending to plug it. From examination of a typical prior art valve arrangement, such as that illustrated in FIG. 12, it can be seen that the problem of accumulation of alumina deposits is exacerbated, in substantial part, due to the partial obstruction of the gate orifice A by the exposed surface B of the tube holder C when the valve operates under throttled or partial flow conditions. Although a restriction in metal flow through the gate can sometimes be compensated by adjusting the position of the gate in order to expand the area of the flow opening, the accumulation of deposits in the gate opening results in gates rapidly becoming inoperative for their intended purpose. Consequently, gates must be changed frequently thereby resulting in an increased cost of production, represented not only by an increased cost of refractory elements for the valve, but also by increased costs attendant with disruption of the teeming operation.
It is to the amelioration of such problems, therefore, to which the present invention is directed.